Horton

Re: Another regexp performance improvement: skip useless paren-captures

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
Cc: Andrew Dunstan <andrew@dunslane.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Joel Jacobson <joel@compiler.org>
Date: 2021-08-08T20:25:00Z
Lists: pgsql-hackers

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Mark Dilger <mark.dilger@enterprisedb.com> writes:
> Hmm.  This changes the behavior when applied against master (c1132aae336c41cf9d316222e525d8d593c2b5d2):

>  select regexp_split_to_array('uuuzkodphfbfbfb', '((.))(\1\2)', 'ntw');
>   regexp_split_to_array
>  -----------------------
> - {"",zkodphfbfbfb}
> + {uuuzkodphfbfbfb}
>  (1 row)

Ugh.  The regex engine is finding the match correctly, but it's failing to
tell the caller where it is :-(.  I was a little too cute in optimizing
the regmatch_t result-vector copying in pg_regexec, and forgot to ensure
that the overall match position would be reported.

Thanks for the testing!

			regards, tom lane

Commits

  1. Fix regexp misbehavior with capturing parens inside "{0}".

  2. Let regexp_replace() make use of REG_NOSUB when feasible.

  3. Fix bogus assertion in BootstrapModeMain().

  4. Avoid determining regexp subexpression matches, when possible.

  5. Check the size in COPY_POINTER_FIELD

  6. Make regexp engine's backref-related compilation state more bulletproof.